"I know that he's starting to get a little fatigued," Collins said. "He's fine to pitch, but that's why I'm going to try to keep him away from multi-inning save situations -- because it's still May and this guy's pitched so many games that aren't closing [situations]."

Parnell has appeared in 18 games this season, but only six for save opportunities. He has an 0.98 ERA in 18 1/3 innings, with 16 strikeouts and a 4-0 record. Collins praised Parnell, saying if it was up to the pitcher and not the manager, there would be no restriction on his workload.

"He wants to be out there," Collins said. "Right now, he wants to be out there when the game's on the line. And he doesn't care if it's the seventh inning, the eighth inning or the ninth inning."

He was recalled last week and has been a pleasant surprise, allowing just one hit and one walk in 2 2/3 innings over the last three appearances.

"In the three games he's pitched since he's been back, I've seen much more confidence in his stuff -- much more confidence in his delivery," manager Terry Collins told MLB.com Saturday. "This is a new thing to him. But I thought the ball is getting more movement to it than it was before. I think his offspeed stuff is better than it was in the beginning."

The decision previously was put on hold due to the possibility that one or both of those pitchers could have been needed in the bullpen.

"We're good, we're fresh down there," manager John Gibbons said of his bullpen. "[Jenkins] was in case something happened to Buehrle really early or something."

The knee injury happened May 7 in St. Petersburg, Fla., in the same game he was struck in the head by a line drive off the bat of Tampa Bay's Desmond Jennings.

"His head is feeling fine, his knee is bothering him a little bit," manager John Gibbons said. "When he fell after getting hit he twisted his knee, so that's the big concern right now. Somebody's looking at it all the time but no more X-rays. It's just one of those things that's just going to take time. He'll be a while."

Barton, 27, was hitting .143 with a homer and three RBI over 21 at-bats. 

Zambrano is on a minor-league contract and has no promise from the team about earning a promotion, but he does have a July 1 opt-out on his contract. 

"Well, we haven’t seen a lot of improvement. He has started to hit the ball a little harder the last four or five days," Alderson said. "It wasn’t until late May last year that we even addressed the topic with him. But it's important for him to just have good at-bats. I told him don’t worry about results right now."

Despite publicly acknowledging that the organization has discussed demoting Davis to Las Vegas, Alderson said that the team will not be forced into making a decision if Davis has not turned things around by a certain date.

“There is no timetable on Ike,” Alderson said.